Homopolar magnetic circuit



R. V. MORSE.

AGNETIC 4CIRCUIT.

ROBERT v. MORSE, OE ITHACA, NEW YORK.

HOMOPOLR MAGNETIC CIRCUIT.

specification of Letters Patent.

Patented Jan. e, reso.

.application filed September 13, 1917. Serial No. 191,267.

mentof a lighter and more compact field magnet structure' while maintaining a substantially nuniform iiux distribution in the active areas of the homopolar fields.

In the drawings forming part of this specification, Figure I is a vlongituc'linal cross-section, partly inr elevation, on theline I-I of Fig. II, lshowing a homopolar machine and one view of the magnetic circuit.

Fig. II is a cross-section on the plane II-II of Fig. I.

Fig. III is a cross-section, on a smaller scale, taken on the plane III-III of Fig. I,-showing another view of the magnetic circuit.

Fig. IV is a diagram illustrating one method of connecting the brushes.

As shown in the drawings, the cylindrical armature 1 mounted ,onfthe shaftQ, has on or near its cylindrical surface two belts or zones of conductor bars 3, 3', each vzonev extending entirely around the armature and being made up of a large number of the armature conductors extending axially. Bordering at each side of each armature conductor zone 3, 3 is a belt of collector segments 4, 4', 4:, 4,similar in appearance to commutator segments, though the operation of the machine does not involve I commutation.

'Each armature vconductor bar 3, 3 has at each end a separate collector segment 4, 4, etc., all beinginsulated from the armature core and from each other.

The armature conductors 3, 3 are generally concealed under' binding .Wire '5, shown partly torn away in Fig. I in order to reveal the armature conductors beneath. The collector segments 4 are held in place by the locking means 6 which allows them to be readily replaced in case of wear without dismantling the machine. The outer ends 7, 7 of the armature core lare generally left bare.

Surrounding the armature and extending substantially the full length thereof is the field structure 48. This field structure 8 is characterized by a number of lobes or risers 9 Vextending in the manner of large ridges or corrugations longitudinally of the machine. T he machine illustrated in the drawings has for example six such risers 9. bases of these risers 9 spread out and join each other some distance outside of the armature face, so that the armature 1 is completely encircled by theA eld structure in the region of thezones 3, 3 and the end faces 7, 7 as illustrated in the lower half of Fig. I Where these encircling rings. or annularpolefaces of the ield structure appear in cross-section. In the region of the collector segments 4, et', 4, fi", sets of brushes 10, 10, 10,'10, are arranged',each set of brushes encircling the armature as shown in Fig. II, the

spaces between the brushes being only suiicient to prevent short-circuiting through a collector segment. Connecting the brushes 10 at one side iof a Zone 3 lto the brushes 10 'at the other border thereof are the stationaryconductors 11. Similarly for the other zone 3 the stationary conductors l1 connect the-brushes v10 and 10.' These stationary conductors may be arranged to con- The the current might enter the armature conductors 3 through the brush a, pass through the armature conductors 3 to the brush b,

and out from the brush b through the stationary conductor 0,' into the armature conductors 'again throughthe brush al, out at the brush e, back through the stationary conductor f, and so on. ,i

The spaces occupied bythe four sets of brushes, 10, 10 and l0, 10', form three continuous channels in the eld structure' encircling the armature,-the two brush sets l0', 1-0` in the middle lying in a channel of double width. These brush chan- 4 nels are accessible through where they open into the hollows between the risers 9, and the brushes may thus be inspected and adj usted. The risers 9 themselves, or the outer partsthereof, bridge over the brush channels as shown in the upper part of Fig. I, forming the bridges 12,'-shown in cross- -section in Fig. II. These bridges are necessary to. complete the magnetic circuit, which goes in general from the armature to the pole face, then up through the riser 9, across through the bridge 12, Adownthrough the iee A riser 9 to the pole face, and into the armature again at the other zone, and then longitudinally through the armature core to the zone from which we started. The magnetic circuit is the same in each of the risers 9 of Fig. II all around the armature, and is indicated by the circles nof arrows in the upper half of Fig. I. This gives a homopolar field (i. e. of the same polarity all 10 the way around the armature), at the armature zone 3, and a second homopolar field of opposite polarity for the zone 3. The direction of the magnetic flux on the plane 111-,

III is shown for example in Fig. III,- where the arrows pointing inward from all sides indicate the magnetic flux in the zone 3. Conversely, the flux would be outward at al1 parts of the zone 3. The flux in the armature core lieslin general in axial planes as is charactertistic of all homopolar machines,-instead of in radial planes as in the ordinary bi-polar or multi-polar types. The two outer magnetic circuits indicated in Fig. I supplement the middle magnetic circuit, combining with it to give broad homopolar iields permitting longer armature conductors in the zones- 3, 3 than would otherwise be desirable. The magnetic circuits may be energized by the exciting coils 13 around each of the bridges 12, or by single coils 14, 14 embedded in the field structure 8 and encircling the arma- -ture 1. f

As the armature is rotated, the conduc` '35 tors of the armature'zones 3, 3 cut the magnetic iux of the hoinopolar fields, generating an electro-motive force which is constant in 'direction throughout each zone. When an external circuit is completed, the 40 current then flows through the armature conductors, brushes, and,l stationary conductors, in the manner described.

The arrangement of the field and armature circuits described are treated more particularly in the Patent No. 1,271,061, for dynamo-electric machine, granted to me July`2, 1918, and the particular improvements herein claimed relate to the field strucl ture of the machine. Since an exciting coil encircling the armature will produce homopolar fields, the leads from the brushes can also be-made to act as an exciting coil, by inclining. or extending the leads so that the current in them flows in the same general direction as inthe exciting coil. Such an inclination of the leads is shown for example in Fig., II, allextending in the same Way because-the current flows in the same direction in them all. rIfhe leads going downto the brushes at the other side of .the armature' .'zoneextend the same way, since the current there iows to instead of from the brushes, thus giving the opposite flux direction there desired. It has been known that .the leads of a homopolar machine, if extended in the direction of an exciting current, would make the machine to some extent self exciting, thus aiding or supplanting the regular exciting coils. My invention herein described goes further and utilizes, not only the inclined leads which extend in planes generally transverse the machine as in Fig. II, but also uses the stationary conductors 11'extending longitudinally of the machine and connecting the inclined leads,--that is, the

conductors which extend in general parallel to the axis of the machine from one brush channel over to another brush channel.

It will be observed that the flux which passes as a unit through the armature core in the plane II-II for example, is split up into say six parts in passing back through the bridges 12, since these bridges are necessarily separted from eachother in order to allow access to the brushes. The bulk 0i' the flux naturally tends to take the shortest iron path and so has a tendency to make the magnetic field stronger directly under each bridge 12 than it is under thehollows 90 between bridges. Such an unbalanced flux tends to cause unbalanced currents in the armature` conductors and eddy currents in the armature core. Hence it is desirable that the iux be of substantially uniform density at all points of the armature circumference. If the annular pole faces are sufficiently thick the flux will spread out univformly in them; but it is desirable to have the bridges as near the armature as possible, and t0 have the pole faces limited in thicks ness, in order to reduce the size and weight of the machine. The primary object of this invention is to aid the flux in spreading out in the pole faces, in order to thus reduce the size of the machine.

It will be noted on inspection of Fig. II and Fig. III that the risers 9 are curved or tapered outward on the side where the stationary conductors 11 pass,-while on the other 110 side the risers extend in comparatively straight. It has been seen that the inclined leads fromthe brushes strengthen the magnetic iux,-for example, may tend to send the iux inward; in which case the current iowing longitudinally in the stationary conductors 11 creates a local flux around said conductors tending to throw the main flux to the right, so as to fill out the spreading portion at the base of the riser 9. In other words, by suitably curving one side of the risers- 9 and throwing the stationary return conductors 11 across that side, the resulting flux is given a somewhat oblique path from the risers to the pole faces, as shown 125 in Fig. IIL-and thus the tendency of the iux to iunduly concentrate directly under the bridges is obviated and a more uniform iux distribution is obtained in a compact machine. In this 'manner the local eld 12,0

existingaround the longitudinal' return con# ductors 11 is utilized to assist in distributing 'the magnetic flux of the main fields,-so that substantial uniformity results 'even when the eld structure is made quite compact.

gular exciting coil around the base of each riser,-thus aiding excitation.

Another advantage of. extending the ref turn vstationary conductors along the sloping side of such a riser or corrugation 9 will be seen if the density inthe magnetic circuit is followed through, inch/by inch. It will be seen that the maximum lux density will generally occur in the neighborhood of the base of the risers 9. This is the point then Where it is most desirable to spread out the iiux through all the avail able iron so far as possible.

The arrangement of the magnetic circuits disclosed above has been described yby Way of illustrationin connection with a bihomopolarv machine having supplementary unil polar fields; but it will be obvious to those skilled in theart that similar arrangements may be used on any homopolar or unipolar machine, regardless of the number of bridges or of the number of effective fields involved. Hence the invention should not .be understood as limited to the precise form of machine shown, nor to that precise arrangement and contour of the field structure.

I claim as my invention: f

l. In a homopola-r dynamo-electric machine, an armature of the cylindrical type, a zone of armature conductors, belts of collector segments bordering the zone, a band of closely spaced brushes extending around each belt -of collector segments and bordering the zone of armature conductors, a field structure providing a liomopolar pole face for said Zone and having annular channels in which the brushes are located, the iield structure having a number of ridges and hollows extending in a substantiallyT axial direction, the hollows communicating with the brush channels, the ridges bridging over the brush channels and merging into the homopolar' pole face, and stationary conductors connecting the brushes bordering one side of the Zone to the brushes bordering the other side, said' stationary conductorsV extending longitudinally in the hollows ofv .the ield structure and being'inclined at each end in such a direction as to excite the homopolar iield.

2. In a homopolar dynamoelectric machine, a ield structure having a number of ridges yand holloWs extending in a longitudinal axial direction, the ridges having substantially 'straight faces on one side and faces extending outwardly from the base on the other side, and electrica-l conductors extending longitudinally in the hollows betwe'en the ridges.

rIn witness whereof AI have hereunto set day of September, 1917.

my hand this '7 th ROBERT V. MORSE.

Witnesses:

ELM'ER H. vWANZER, J. S. BARR.v 

